FIG. 14 shows a conventional LED illumination system 400 described in e.g. Patent Document 1 and Patent Document 2. As shown in FIG. 14, in a conventional LED illumination system 400, a ballast 402 (fluorescent lamp lighting device) of an existing straight-tube fluorescent lamp luminaire 401 (hereinafter sometimes referred to merely as “luminaire”) is removed and, in its stead, a LED lighting device 403 is installed. As to the wiring, input electric wires 404 from a commercial power supply to the ballast 402 and output electric wires 406 from the ballast 402 to two sockets 405 on both ends are directly connected to the LED lighting device 403. Furthermore, the conventional LED illumination system 400 comprises a LED lamp 407 (hereinafter sometimes referred to merely as “lamp”) installed between the sockets 405, said LED lamp 407 having LEDs (Light Emitting Diodes), being constructed to have its end structure (bases, base pins, etc.), its dimensions, etc. matched to the whole length of a straight-tube fluorescent lamp, and, as a whole, assuming a shape similar to that of a straight-tube fluorescent lamp, so that it can be attached to two sockets 205 on both ends.
When a predetermined voltage is applied to the LED lighting device 403 from the commercial power supply via the input electric wires 404, electric power is supplied from the LED lighting device 403 to bases 407a and 407b on both ends of the LED lamp 407 via the sockets 405 on both ends. Then, the installed LEDs emit light and are used for illumination.
According to Patent Document 1, an adapter for identification is provided between the sockets 405 and the bases 407a, 407b. This adapter is inserted for the purpose of identifying a currently used straight-tube fluorescent lamp.
According to Patent Document 2, the bases 407a and 407b are insulated and used only for supporting the LED lamp 407, lead wires are provided seperately, and thus, the LED lighting device 403 and the LED lamp 407 are electrically connected.
In case of a straight-tube fluorescent lamp, both ends of filaments provided on both its ends must be further connected independently to the ballast 402 (fluorescent lamp lighting device). Therefore, two output electric wires 406 and two terminals in the socket 405 are needed on each side. Namely, four output electric wires and four terminals in the sockets are needed in total for both sides.
On the other hand, for the LED lamp 407, basically, two independent connections suffice. However, the LED lamp 407 shown in FIG. 14 is constructed by combining a straight-tube fluorescent lamp with an end structure (base, base pins, etc.). Herein, for example, one of the two base pins on one side is a dummy base pin. Thus, in the case where the LED lamp 407 is connected to the two output electric wires 406 and the two terminals in a socket 405 on each side, which totals four of each for both sides, it may in some cases not be possible to connect the LED lighting device 403 to the LED lamp 407, depending on the insertion direction.
As one example for preventing the above problem, electric power is supplied to both ends, and a short circuit is created in the LED lighting device 403 or the LED lamp 407 beforehand, so that the respective two of the four output electric wires that are connected to the same socket 405 are set to the same electric potential.
Since it is necessary to operate the LED with a direct current and in such a manner that the current is controlled, the above LED illumination system requires an AC-DC conversion means, a voltage conversion means and a current control means between the commercial power supply and the LED. Depending on how these means are allotted on the luminaire side and the lamp side, the following types emerge.
In the “First Type”, almost all means are located on the luminaire side and a controlled direct current is supplied to the lamp side.
In the “Second Type”, the AC-DC conversion is performed on the luminaire side and a voltage with an appropriate value is supplied to the lamp side, while the lamp side has the current control means.
In the “Third Type”, the current passes through the luminaire side almost without stopping and the lamp side has almost all the functions.